The mechanisms of defect accumulation and dynamic annealing in ion-implanted crystalline and amorphous Si are elucidated by performing conductivity and Raman spec-trascopy measurements in-situ during ion irradiation. In amorphous Si the entire gamut of defect structures has been characterized by analyzing the annealing kinetics from 77 K to ~ 800 K both during and after irradiation. Moreover the modifications in the electronic properties of crystalline Si produced by ion-irradiation have been investigated. The use of in-situ techniques in combination with transmission electron microscopy and deep-level transient spectroscopy allowed us to demonstrate the correlation between structural and electrical defects produced by ion-irradiation in Si.

Ion damage processes and amorphous phase formation are compared in Si, GaAs and Alx Ga1-x As materials in the critical regime where dynamic defect annealing is strongly competing with ion damage production. It is shown that the nature of residual damage is very strongly dependent on temperature, ion dose and dose rate in this critical regime for both Si and GaAs and that the amorphous phase can be “nucleated” by high levels of extended defects. In Alx Ga1-x As, the amorphous phase is increasingly more difficult to nucleate with increasing Al concentration at LN2 temperature but can be nucleated at sufficiently high implantation doses for all Al concentrations. No dose rate effect is observed for Alx Ga1-x As. This behaviour is discussed in terms of the availability of mobile defects and bonding configurational changes during irradiation.

The microstructures of Si ion-implanted with Cu have been characterized by TEM after annealing. For 1.2 at.%, the Cu is trapped at planar defects, but for 10 at.%, η-Cu3Si forms, allowing Cu to diffuse at its equilibrium solubility. These observations allow proper evaluation of the binding energies of Cu to previously formed internal cavities (2.2 eV) and η-Cu3Si (1.7 eV). The η-Cu3Si in the 10 at.% layer catalyzes oxidation of the Si. The microstructures also indicate that Si implanted with ~2 at.% Cu reforms epitaxially with embedded defects after 8 hr. at 700°C, but for ~10 at.% Cu, epitaxy is not recovered after 6 hours at 600ºC.

Cavities formed in Si by He ion implantation and annealing are shown be strong traps for Cu and Ni impurities. Experiments utilizing ion-beam analysis and transmission electron microscopy indicate that Cu is trapped at the internal surfaces of cavities up to ≈1 monolayer coverage with a binding energy of 2.2±0.2 eV relative to solution. This is greater than the heat of solution from the precipitated Cu3Si phase, determined to be 1.7 eV in agreement with earlier work. Copper at cavity-wall sites is reversibly replaced by H during heating in H2 gas, indicating the relative stability of the two surface terminations. Initial results for Ni impurities indicate that trapping at cavities is again energetically preferred to suicide formation. The saturation coverage of Ni on the internal surfaces, however, is an order of magnitude smaller for Ni than Cu, consistent with published studies of external-surface adsorption. These results suggest that cavity trapping may getter metallic impurities in Si more effectively than methods based on suicide precipitation.

Variable energy positron annihilation and Rutherford backscattering spectroscopy have been used to investigate the evolution of secondary defects during the annealing of self-ion irradiated silicon. Evidence supporting the existence of both vacancy- and interstitially-based defects after high temperature anneals is presented. Dopant type and irradiation temperature have both been shown to influence the structure of the defects whose onset can be manipulated via the implantation flux.

Single crystal, type IIa natural diamond substrates have been implanted with 4 MeV carbon ions to doses ranging from 0.5–130×1016 cm-2. The accumulation of implantation damage is studied by Raman and RBS/channeling. Similar effects are observed for crystals of [100], [110], and [111] orientation but with different rates of damage accumulation. With increasing implantation damage, the triply degenerate Raman mode at 1332 cm-1 broadens and shifts down to around 1300 cm-1. This corresponds to a peak in the one-phonon density of states as predicted for Raman from an amorphous sp3 network. There is no evidence for the existence of sp2 carbon in the implanted area. Additional non-graphite Raman peaks appear at 1451, 1494, and 1635 cm-1. At the higher doses, the 1332 cm-1 Raman mode is no longer observed; however, RBS/channeling still shows the surface region to be crystalline and it is possible to grow high quality homoepitaxial diamond films on these substrates.

Arsenic precipitates can be formed in GaAs using arsenic implantation and annealing, thereby producing very high resistivity (surface or buried) GaAs layers. Arsenic-implanted materials are similar to low-temperature (LT) GaAs:As buffer layers grown by molecular beam epitaxy (MBE) which are used for eliminating side- and backgating problems in GaAs circuits. Arsenic implantation is not only a simple and economical technique for device isolation but also can improve the quality of individual devices. Through surface passivation, arsenic implantation can reduce gate-to-drain leakage in and enhance the breakdown voltage of GaAs-based metal semiconductor field-effect transistors (MESFETs) and high electron mobility transistors (HEMTs). High resistivity thin surface layers may be used as gate insulators for GaAs-based metal insulator semiconductor (MIS) FETs, leading to the development of a novel GaAs-based complementary metal insulator semiconductor (CMIS) technology like advanced Si-based complementary metal oxide semiconductor (CMOS) technology but with higher radiation hardness and operational speed.

Radiation-induced segregation (RIS) in Ni-12.7% Si and Cu-1% Au alloys was studied using Rutherford backscattering spectroscopy during He and Ne irradiation at elevated temperatures. During single ion-beam irradiation with 1.5 MeV He, strong RIS of Si toward the surface was observed in Ni-12.7% Si. Simultaneous irradiation with 400 keV Ne and 1.5 MeV He almost completely suppressed the Si segregation, even when the calculated damage production rate by Ne was only a few percent of that by He ions. A similar effect of dual-beam irradiation was observed in the Cu-1% Au alloy, i.e., the rate of near surface Au depletion was strongly reduced under simultaneous irradiation. The present result shows that dual-beam irradiation can be applied to control RIS and RED (Radiation Enhanced Diffusion) during ion beam processing.

Different behaviors of the normal-state resistivity have been observed in (110)-, (113)- and a-oriented YBa2Cu3O7-δ thin films under 200 keV H+ irradiation. It suggests that the c-axis electrical conduction is very sensitive to nonoxygen point defects and a ”semiconductor-metal” phase transition could be induced at very low densities of these defects.

We have studied the damage kinetics in single crystal MgAl2O4 (spinel) with (100) orientation under 370 keV Xe ion irradiations at temperatures of -100 and 400 C. In-situ Rutherford Backscattering Spectrometry (RBS) and ion channeling have been used to monitor the damage accumulation in spinel following sequential Xe ion irradiations. A significant temperature effect on the irradiation damage has been found. Channeling data show that at -100 C, the irradiated spinel layer reaches the same level as in a random spectrum at a dose of 8×1015 Xe/cm2 (20 DPA for peak damage), while at 400 C, the near surface region (50 nm) remains single-crystalline up to 2×1016 Xe/cm2.

The mechanical and electronic properties of ion implanted polymers have been determined to be a function of ion dose, energy and beam current. In previous studies the implant layer was assumed to be isotropic. In an earlier report we speculated that the implant layer was not isotropic, based on a temperature coefficient of resistivity (TCR) that could not be explained by a single structural configuration[1]. In this study we examined the effect of etching the surface layer, decreasing polymer thickness, on the TCR to determine which part of the implant layer contributed to the various mechanisms of conduction. We have concluded that there are at least two mechanisms responsible for conduction, Mott three dimensional variable range hopping(VRH), and Mott one dimensional VRH. It is possible that other theories may be more correct (e.g. crossover to ES-VRH at low temperatures) since many theories predict the same temperature dependence. We found that conduction with the Mott one dimensional VRH exists at the bottom of the implant layer.

The development of the damage structure produced in (100) GaAs/Al0.6Ga0.4As/GaAs by 1 MeV Kr+ ion irradiation at 77 and 293 K has been investigated by RBS channeling and cross-sectional high-resolution TEM techniques. Following an implantation to a dose of 1014 ions cm-2 at 77 K, RBS channeling spectra indicate that the Al0.6Ga0.4 layer contained a high defect density and was possibly amorphous. Warming to room temperature resulted in a change in the channeling spectrum, which indicated that the damage in the Al0.6Ga0.4As layer had partially recovered. The degree of recovery was greatest at the GaAs/ Al0.6Ga0.4As interface, and decreased with increasing depth. TEM observations show the damage in the Al0.6Ga0.4As to be comprised of planar defects, the density of which increases with depth, and an amorphous layer at the bottom interface. This difference in the damage distribution is consistent with the asymmetry in the channeling spectrum. A model based on the depth variation of cascade density is proposed to account for the observations.

Raman spectra excited at two laser wavelengths are used to study the damage in self-implanted silicon. It was found that the contributions from the damaged surface crystalline and a-Si layers can be distinguished and separated, based on the different light absorption coefficients. A defect-activated low frequency band in the damaged surface crystalline Si layer was revealed. In totally amorphized samples the Raman spectra excited by 457.9 and 647.1 nm show different scattering intensity ratios for the optical- and acoustic-like-phonons. This novel result seems to indicate a depth dependent variation of the disordering in the amorphous layer.

Electron beam irradiation at energies between 0.5 and 4 keV has been found to produce defects in oxide materials including SiO2, Al2O3 and ZrO2. These defects trap excess charge in the materials and affect their electronic and optical properties. Measurements of the thermally stimulated exoelectron emission following irradiation provides information on relative defect concentrations, defect creation mechanisms, electron trap binding energies, electron emission mechanisms and annealing properties of these materials. Electron emission during sample heating occurs via a variety of mechanisms including the thermionic emission of excess charge from defects at temperatures characteristic of each trap binding energy. By measuring relative trap concentrations as a function of beam parameters, we have identified electron beam energy thresholds for the creation of some types of defects which correlate with core level electronic transitions. Also, electron emission which occurs during defect annealing or diffusion to a surface shows the conditions for the elimination of defects. The ability to control and characterize defect formation and annihilation provides the possibility of engineering specific surface defect conditions. In addition, defect creation by electronic processes is very selective as compared with momentum transfer in ion beam damage of surfaces.

We have investigated the densification behavior of sol-gel zirconia films resulting from ion irradiation. Three sets of films were implanted with neon, krypton, or xenon. The ion energies were chosen to yield approximately constant energy loss through the film and the doses were chosen to yield similar nuclear energy deposition. Ion irradiation of the sol-gel films resulted in carbon and hydrogen loss as indicated by Rutherford backscattering spectrometry and forward recoil energy spectroscopy. Although the densification was hypothesized to result from target atom displacement, the observed densification exhibits a stronger dependence on electronic energy deposition.

The influence of in-situ electronic perturbations on defect generation during 150 keV proton implantation into biased silicon p-n junctions has been investigated. The concentration and spatial distribution of the deep traps were characterized using a modification of the double corelation deep level transient spectroscopy technique (D-DLTS). With the in-situ electric field applied, a decrease in concentration of vacancy-related, as well as H-related, traps was observed. 500 keV He+ implantation was also performed to supplement the above studies and to differentiate any passivation effects due to hydrogen. A model based on the charge states of hydrogen and vacancies was used to explain the observed behaviour.

Damage depths for Ar-implanted fused silica have been examined by Rutherford backscattering (RBS) and elastic recoil detection (ERD) ion-beam analysis. H incursion (6 at. %) from ambient atmospheres to twice TRIM values was found for damage depths which intersected the surface. H implants were used to decorate Ar damage for deeper Ar implants. The incursion of H for high-fluence implants is important for optoelectronic applications.

Changes in the resistivity of n-type InP and InGaAsP by He+ ion implantation have been investigated at implant temperatures of 60-523K. The highest resistivities are achieved at the lowest temperatures under the conditions where the dose is sufficient to render the implanted region amorphous, as indicated by Rutherford backscattering/channeling measurements. Anneal data indicates that the high resistivities achieved via amorphization are stable to higher temperatures than when the samples remain crystalline after implantation.

An arsenic atom displacement in As+ ion implanted Si induced by He+ ion beam irradiation has been studied by medium-energy (175keV) ion spectroscopy (MEIS). The He+ energy and dose dependences of the displaced arsenic atoms have been examined in the range of 30-175keV and ≤6×10-4C/cm2, respectively. The amount of the displaced arsenic atoms are found to be proportional to the dose and inversely proportional to the nuclear stopping power in the low-dose region, while it saturates at high-dose region. The dose-proportional region is composed of two different proportional coefficient segments.

Utilization of radiation damage by means of ion implantation to reduce parasitic capacitances in GaAs integrated circuits has become a well-established technique in the last years. Similar to GaAs, novel high-speed silicon-based devices, e.g. the Si/SiGe heterojunction bipolar transistor, are generally marked by additional short time annealing related to doping activation and a metallization annealing step in the range of 400 °C .

For reproducing the external base region of such devices, Si-p+nn+ diodes were realized and investigated using I-V and C-V measurements. Slight radiation damage was achieved by Ne-implantation. Apart from enhanced leakage currents due to space charge recombination, capacitance reduction for frequencies above 50 kHz was observed even for a n-layer doping concentration as high as 1 to 2x1017 cm-3 including a 12 min 400 °C annealing step. Preliminary tests with 250 keV-Ne-ions within a dose range between 1013 and 1014 cm-2 were carried out with Schottky diodes on moderately doped n-type Si-substrate (0.3 Ωcm). For a high temperature furnace anneal at 900 °C (2 min), no capacitance reduction could be observed.

Compared to previous results with Ar-implantation to obtain amorphized silicon layers, this technique allows a more easy technological handling concerning the metallization and the use of a simple photoresist pattern.